(1) Field of the Invention.
Various imaging technologies, whether analogue or digital, are widely used in medical applications to capture images of internal structures of a body and particularly bones. In some applications, it can be useful to capture multiple images of a body part. In some applications, it does not matter if the body part moves between image captures. However, in other applications it can be important that the body part remains stationary between image captures. For example, in applications in which images of the same body part from different directions are required, it can be important that there is no movement of the body part between image captures, otherwise, it can be difficult to determine whether a feature in the image is a genuine feature of the body part or an artefact created by movement of the body part between image captures.
For example, multiple X-ray images of the same body part can be used to instantiate a statistical shape model of the body part. If there is movement of the body part between X-ray image captures, then the instantiated model may be less accurate, as it is trying to fit to an artefact in the image data set, rather than to the pure image data.
Fiducials with a known geometry can be used so that the position of the body part relative to the fiducials can be determined from captured images including the fiducials. However, in the time that passes between the acquisition of two projection images, the subject may move with respect to the fiducials that are to be used to register the image into one coordinate system. This may occur when imaging soft tissues, e.g. the heart, or when imaging extremities like legs or arms, if the fiducials are not rigidly attached to the object of interest. For example, in pre-operative bone model calculation, the calibration object can sometimes not be attached rigidly to the body part (especially in obese patients, or for the pelvis, the femur, humerus, etc.).
In the case of movement of a rigid body part, e.g. a bone, and few images, the motion artefact may not easily be recognized, and an incorrect reconstruction of the imaging system geometry may occur.
(2) Description of Related Art
US Patent application publication number US 2005/0220264 A1 describes a technique in which projection images are corrected to nullify any motion. However, image correction often results in errors due to interpolation artefacts.
Hence, it would be advantageous to be able to reduce the existence of artefacts in image data resulting from movement of a body part between image captures.